Field of the Invention
The invention relates to bisphosphites having a central 2,3′-biphenol unit. In addition, the use thereof as ligands in hydroformylation.
Discussion of the Background
A bisphosphite has a central unit, called the backbone, and two outer units bonded to the central unit via the phosphorus atom.
The compounds according to the invention have a central 2,3′-biphenol unit.
A 2,3′-biphenol unit is understood to mean a biphenol unit having the following structure:

The numbering of the carbon atoms in the rings in the IUPAC name of the compound may lead to different position figures from 2 and 3 depending on additional substituents.
The reactions between olefin compounds, carbon monoxide and hydrogen in the presence of a catalyst to give the aldehydes comprising one additional carbon atom are known as hydroformylation or oxo synthesis. The catalysts used in these reactions are frequently compounds of the transition metals of group VIII of the Periodic Table of the Elements. Known ligands include, for example, compounds of the phosphine, phosphite and phosphonite classes each comprising trivalent phosphorus PIII. A good overview of the state of the hydroformylation of olefins can be found in B. CORNILS, W. A. HERRMANN, “Applied Homogeneous Catalysis with Organometallic Compounds”, vol. 1 & 2, VCH, Weinheim, N.Y., 1996 or R. Franke, D. Selent, A. Börner, “Applied Hydroformylation”, Chem. Rev., 2012, DOI: 10.1021/cr3001803.
Every catalytically active composition has its specific benefits. According to the feedstock and target product, therefore, different catalytically active compositions are used.
U.S. Pat. Nos. 4,694,109 and 4,879,416 describe bisphosphine ligands and use thereof in the hydroformylation of olefins at low synthesis gas pressures. Particularly in the case of hydroformylation of propene, ligands of this type achieve high activities and high n/i selectivities (n/i=the ratio of linear aldehyde (=n) to branched (=iso) aldehyde). WO 95/30680 discloses bidentate phosphine ligands and the use thereof in catalysis, including in hydroformylation reactions.
It is a feature of most of the bisphosphites known in the prior art that they have a 2,2′-biphenol as central unit, i.e. in the backbone. The use of a 2,3′-biphenol as central unit is entirely unknown.
Even though a multitude of ligands and the use thereof in rhodium-catalysed hydroformylation are known, it is desirable to develop new ligands having improved properties.